title: Occlusal trauma accelerates attachment loss at the onset of experimental periodontitis in rats.
abstract: OBJECTIVE
  Occlusal trauma is an important factor that influences the progression of periodontitis, but it is unclear whether occlusal trauma influences periodontal destruction at the onset of periodontitis. We established an experimental periodontitis model with both site-specific loss of attachment and alveolar bone resorption. The purpose of the present study was to investigate the effects of occlusal trauma on periodontal destruction, particularly loss of attachment, at the onset of experimental periodontitis.
  
  
  METHODS
  Sixty rats were used in the present study. Forty-eight rats immunized with lipopolysaccharide (LPS) intraperitoneally were divided into four groups. In the trauma (T) group, occlusal trauma was induced by placing an excessively high metal wire in the occlusal surface of the mandibular right first molar. In the inflammation (I) group, periodontal inflammation was induced by topical application of LPS into the palatal gingival sulcus of maxillary right first molars. In the trauma + inflammation (T+I) group, both trauma and periodontal inflammation were simultaneously induced. The PBS group was administered phosphate-buffered saline only. Another 12 nonimmunized rats (the n-(T+I) group) were treated as described for the T+I group. All rats were killed after 5 or 10 d, and their maxillary first molars with surrounding tissues were observed histopathologically. Loss of attachment and osteoclasts on the alveolar bone crest were investigated histopathologically. To detect immune complexes, immunohistological staining for C1qB was performed. Collagen fibers were also observed using the picrosirius red-polarization method.
  
  
  RESULTS
  There were significant increases in loss of attachment and in the number of osteoclasts in the T+I group compared with the other groups. Moreover, widespread distribution of immune complexes was observed in the T + I group, and collagen fibers oriented from the root surface to the alveolar bone crest had partially disappeared in the T, T+I and n-(T+I) groups.
  
  
  CONCLUSIONS
  When inflammation was combined with occlusal trauma, immune complexes were confirmed in more expanding areas than in the area of the I group without occlusal trauma, and loss of attachment at the onset of experimental periodontitis was increased. Damage of collagen fibers by occlusal trauma may elevate the permeability of the antigen through the tissue and result in expansion of the area of immune-complex formation and accelerating inflammatory reaction. The periodontal tissue destruction was thus greater in the T+I group than in the I group.
authors.affiliation: Department of Periodontology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan; Global R&D - Personal Health Care, Kao Corporation, Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Nakatsu
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshinaga
authors.forename: A
authors.initials: A
authors.lastname: Kuramoto
authors.forename: F
authors.initials: F
authors.lastname: Nagano
authors.forename: I
authors.initials: I
authors.lastname: Ichimura
authors.forename: K
authors.initials: K
authors.lastname: Oshino
authors.forename: A
authors.initials: A
authors.lastname: Yoshimura
authors.forename: Y
authors.initials: Y
authors.lastname: Yano
authors.forename: Y
authors.initials: Y
authors.lastname: Hara
mesh_terms: D016301:Alveolar Bone Loss / Q000209:etiology / Q000473:pathology; D000539:Alveolar Process / Q000473:pathology; D000818:Animals; D000936:Antigen-Antibody Complex / Q000032:analysis; D003094:Collagen / Q000032:analysis; D003238:Connective Tissue / Q000276:immunology / Q000473:pathology; D003769:Dental Occlusion, Traumatic / Q000150:complications*; D004195:Disease Models, Animal; D018450:Disease Progression; D004846:Epithelial Attachment / Q000276:immunology / Q000473:pathology; D004926:Escherichia coli; D007074:Immunoglobulin G / Q000097:blood; D008070:Lipopolysaccharides / Q000276:immunology; D008297:Male; D024101:Mitochondrial Proteins / Q000032:analysis; D009504:Neutrophils / Q000473:pathology; D010010:Osteoclasts / Q000473:pathology; D017622:Periodontal Attachment Loss / Q000209:etiology* / Q000473:pathology; D010518:Periodontitis / Q000150:complications* / Q000276:immunology / Q000473:pathology; D051381:Rats; D011917:Rats, Inbred Lew; D013997:Time Factors; D014092:Tooth Root / Q000473:pathology
chemical_list: D000936:Antigen-Antibody Complex; C490195:C1qbp protein, rat; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D024101:Mitochondrial Proteins; D003094:Collagen
keywords: attachment loss; experimental periodontitis; histopathological study; occlusal trauma